Kirby Institute, UNSW Sydney, Sydney, Australia.
Centre for Social Research in Health, UNSW Sydney, Sydney, Australia.
J Acquir Immune Defic Syndr. 2021 Aug 1;87(4):1040-1047. doi: 10.1097/QAI.0000000000002691.
Preexposure prophylaxis (PrEP) prevents HIV infection but relies on good adherence at times of risk, termed "prevention-effective adherence." Most studies assess adherence without reference to sexual behaviur, making it challenging to determine if poor adherence coincides with HIV risk.
We examined data from a behavioral substudy of a large-scale PrEP implementation trial in New South Wales, Australia.
Trial participants completed optional brief quarterly surveys, reporting the number of pills taken and sexual behavior with male partners for each day of the "last full week" before each survey. Condomless sex (CLS) was defined as "higher risk" for HIV when with HIV-positive men with detectable/unknown viral loads or unknown HIV status men. Adequate PrEP protection was defined as ≥4 pills for participants assigned male sex at birth and ≥6 pills for participants assigned female sex at birth (including transgender men).
Of 9596 participants dispensed PrEP, 4401 completed baseline and ≥1 follow-up survey. Participants reported on 12,399 "last full weeks": 7485 weeks (60.4%) involved CLS and 2521 weeks (33.7% of CLS-weeks) involved higher risk CLS. There were 103 weeks in which participants did not have adequate PrEP protection and had higher risk CLS: 4.1% of higher-risk CLS weeks (n = 103/2521), 1.4% of all CLS weeks (n = 103/7485), and 0.8% of all observed weeks (n = 103/12,399).
In a large PrEP trial, prevention-effective adherence to PrEP was very high at 99%. Our findings illustrate the importance of measuring pill-taking and sexual behavior in the same period so that prevention-effective adherence can be better estimated.
暴露前预防（PrEP）可预防 HIV 感染，但需要在有风险时保持良好的依从性，即“预防有效的依从性”。大多数研究在评估依从性时都没有参考性行为，因此很难确定依从性差是否与 HIV 风险同时发生。
我们检查了澳大利亚新南威尔士州大规模 PrEP 实施试验的行为子研究的数据。
试验参与者完成了可选的简短季度调查，报告了每次调查前“最后完整周”的每一天所服用的药丸数量和与男性伴侣的性行为。无保护性行为（CLS）定义为与 HIV 阳性、可检测/未知病毒载量或未知 HIV 状态的男性发生性行为时 HIV 风险较高。对于出生时被分配为男性的参与者，足够的 PrEP 保护定义为至少服用 4 片；对于出生时被分配为女性的参与者，包括跨性别男性，足够的 PrEP 保护定义为至少服用 6 片。
在 9596 名接受 PrEP 分配的参与者中，有 4401 名完成了基线和至少 1 次随访调查。参与者报告了 12399 个“最后完整周”：7485 周（60.4%）涉及 CLS，2521 周（33.7%的 CLS 周）涉及高风险 CLS。有 103 周参与者没有足够的 PrEP 保护且有高风险 CLS：高风险 CLS 周的 4.1%（n=103/2521），所有 CLS 周的 1.4%（n=103/7485），以及所有观察到的周的 0.8%（n=103/12399）。
在一项大型 PrEP 试验中，PrEP 的预防有效依从性非常高，达到了 99%。我们的研究结果表明，测量服药和性行为在同一时期非常重要，以便更好地估计预防有效依从性。
